This invention relates generally to valves for modulating the flow of fluid in a fluid or water circulating system and more particularly to a temperature sensitive phase change operated control valve for such circulating system which is responsive to variations in temperature of a fluid in an associated system such as the refrigerant in a heat pump system operatively associated with the fluid or water circulating system.
In many heat pump systems there will generally be an indoor refrigerant-to-air heat exchanger for the space to be conditioned and an outdoor refrigerant-to-water heat exchanger wherein the water from any suitable source operates as a heat sink for delivering heat to or receiving heat from the refrigerant circulating in non-contacting heat exchange relation with the water in the outdoor refrigerant-to-water heat exchanger.
In the outdoor heat exchanger of such heat pump systems the water is circulated to the outdoor heat exchanger by a pump circulating system which in addition to the heat exchanger includes, a circulating pump, a cooling tower, a storage tank and/or a hot water tank. Such heat pump systems are well known and easily purchaseable on the open market.
There may be several indoor coils, one for each of several spaces to be conditioned and a single outdoor coil or there may be not only a plurality of indoor coils but also a plurality of outdoor coils, the piping being so connected as to promote efficiency between the systems to be connected.
Where there are more than one outdoor heat exchanger the circulating pump will supply the water to each of the refrigerants to water heat exchangers in parallel flow.
In the prior art systems, the water flow is delivered in a continuous cycle at a flow rate of about 2 to 3 gallons per minute per ton of cooling capacity.
At this constant rate of water flow, the water temperature must be controlled if efficient operation is to be maintained because when the inlet temperature of the water is about 65.degree. F. and the heat pump is switched to a cooling mode the outdoor refrigerant to water heat exchanger will cause the refrigerant gas to liquify producing "slugging" in the compressor from which potential malfunction and damage will result. Additionally, the refrigerant coil in the outdoor refrigerant to water heat exchanger may become covered with frost and ice which will render it non-functional for the required heat exchange performance.
Conversely, in the heating mode if the water temperature is above 90.degree. F. the refrigerant compressor will overload and malfunction will result.
The present invention seeks to overcome these problems of the prior art devices by providing a thermally actuated phase change operated conrol valve in the pump circulating system which will vary the volume of water flow delivered by the pump circulating system to the outdoor refrigerant to water heat exchanger, irrespective of the water inlet temperature, as a function of the refrigerant temperature entering the outdoor refrigerant to water heat exchanger so as to insure proper loading on the compressor.
Additionally the present invention provides an improved control valve in that the outlet ports which communicate with the outlet means for the control valve are in the form of substantially rectangular slots so that a large change in porting per given amount of valve head stroke is obtainable. This is important in systems where fluid flow is established by circulating pumps of the centrifugal type which delivers the fluid at a relatively low pressure head. Since, a limited amount of stroke is obtainable from a thermally actuated operator this type of porting means produces a large change in the volume of water flow for a small variation in temperature.